FGF23 and Stroke: The general objective of the study Atrial Fibrillation in Relationship to Plasma Biomarkers (AFISBIO II)—NCT04710745 is to assess the predictive ability of novel plasmatic biomarkers (especially apelin and miRNAs) on prevalent/incident AF in patients with high risk for AF and stroke, and to validate predictive models from previous studies based on co-morbidities, age, sex, BMI, NT-proBNP, FGF-23, IGF-1, and IGFBP-1 on prevalent/incident AF in patients with high risk for AF and stroke.